Sliding glass door roller questions.

Actually - let me ask 3 Questions as follow:
1 - What is weight capacity of 81-018 - either 1 wheel or overall pair?
2- Can I use 81-246 with 81-018, both on bottom of a door (really heavy doors) -
or are the wheels different sized ?
3 - Is 80-106 the correct track for above rollers?

6' Sliding Glass Door Track
Product Code: 80-106

Roller Assembly, 1-3/16" Steel BB
Product Code: 81-246

Sliding Patio Glass Door Tandem Roller
Product Code: 81-018